A horizontal merger is a merger between

Two or more firms from different and unrelated markets.Two or more firms at different stages of the production
process.
A producer and its supplierTwo or more firms in the same market.

Correct - Your answer is correct.

Wrong - Your answer is wrong.

Detailed Answer

(d) The requirement is to identify a horizontal merger.
Answer (d) is correct because a horizontal merger is one between
competitors in the same market. Answer (a) is incorrect because
it describes a conglomerate merger. Answers (b) and (c) are
incorrect because they describe vertical mergers.